P9415-R Datasheet

© 2021 Renesas Electronics Corporation

35

May 4, 2021

9.11.1 FOD Parameters in Receiver Mode

For a WPC power loss foreign object detection to function effectively, the receiver must account and compensate for all of their known losses.

Such losses, for example, could be due to resistive losses or nearby metals that are part of the receiver. Because the system accurately

measures its power and accounts for all known losses, it can thereby detect foreign objects because they cause an unknown loss. The WPC

specification requires that a power receiver must report to the power transmitter its received power (PPR) in an RPP. The maximum value of

the received power accuracy

������������ΔdependsonthemaximumpowerofthepowerreceiverasdefinedinTable9.

The power receiver must determine its PPR with an accuracy of ±

������������Δ,andreportitsreceivedpowerasPRECEIVED=PPR+������������Δ.Thismeans

that the reported received power is always greater than or equal to the transmitted power (PPT) if there is no foreign object (FO) present on the

interface surface.

Table 9.

R

ecommended Maximum Estimated Power Loss

Maximum Power (W)

Maximum

������������Δ(mW)

5

350

10

500

15

750

The compensation algorithm includes parameter values that are programmable either internal register or customer configuration table in MTP.

Programmability is necessary so that the calibration settings can be optimized to match the power transfer characteristics of each particular

WPC system to include the power losses of the transmit and receive coils, battery, shielding, and case materials under no-load to full-load

conditions. The values are based on the comparison of the received power against a reference power curve so that any foreign object can be

sensed when the received power is different than the expected system power.

FOD parameters consist of eight sections. Each section is divided by output current and consists of gain and offset to compensate for Rx

internal power loss; each section is also adjusted for Reported Rx power. The following comprises the Rx load current ranges for the FOD

sections.



FOD section [0] is from 0mA to section 0 current mA



FOD section [1] is reserved for test



FOD section [2] is from section 0 current mA to 351mA



FOD section [3] is from 352mA or section 0 671mA



FOD section [4] is from 672mA to 863mA



FOD section [5] is more than 864mA

Section 0 current is the point where the internal rectifier changes bridge configuration from half-bridge to full-bridge. In the default configuration,

If VOUT is set to less than 7V, section0 current is 288mA. If Voutset is higher than 7V, section0 current is 384mA, section2 is not used and

section3 starts from 384mA. There is around ±30mA load current hysteresis for changing the FOD sections. These settings can be changed

using the P9415-R Wireless Power Pro GUI.

The formula of Rx Reported Power is:

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Place the receiver with the P9415-R on the Nok9 FOD transmitter. Ramp the current on the output of the P9415-R in steps of 50mA to 100mA

and monitor power difference between the Nok9 transmitted power and the receiver reported power value. The difference should be within

maximum Power loss delta in Table 9. If the difference exceeds the maximum power loss delta, adjust the FOD gain or FOD offset of that

particular output current section to bring the difference back to within range. The AP can modify the FOD gain and FOD offset by writing to the

Foreign Object Detection Customer Registers (0x68-0x77). In the final product, the AP can use the VRECTON interrupt or battery charger

interrupt as a trigger to update the FOD registers.